1. Field of the Invention
This invention relates generally to a flow segregator for use in a well completion where multiple lateral wellbores drain into a central casing, and particularly to a flow segregator that maintains a separation of the fluids being produced from each lateral wellbore so that the production can be monitored and controlled.
2. Description of the Related Art
Downhole systems are known that are located in an underreamed section of a wellbore, and which provide vertically spaced or stacked drain openings for lateral boreholes that extend outward into a plurality of individual formations. Each drain is formed by a relatively short section of pipe that is pivoted at its upper end to a housing that is included in a large diameter, so-called "mother" casing that extends upward to the surface. When an actuator stem is run down inside the mother casing, its lower end pivots the drain sections or subs outward until their central axes are inclined at a known angle to the axis of the housing. Seals are automatically positioned to confine formation fluid flow to the bores of the drain subs. The drain subs are mounted at vertically spaced points along the housing, and can be angularly spaced so as to extend outward at different azimuths.
Once the drain subs are extended and the housing and the mother casing cemented in place, an oriented whipstock is used to deflect a drill bit outward through each drain sub so that a plurality of deviated boreholes can be drilled out into the formations to efficiently drain the same of production fluids. The whipstock also is used to set a liner string of casing in each deviated borehole, which then is cemented in place. The various cased wellbores then can be completed and put on production. The system can be used in connection with newly drilled wells, or for the re-entry of one or more existing lateral wells.
Although the above-described system is highly useful for efficient drainage of certain formations, it has the disadvantage that the production fluids coming in through each drain sub are intermixed and commingled in the housing and the mother casing. If one lateral wellbore is producing mainly salt water, for example, this fluid will contaminate the oil being produced from the other lateral wellbores. It may not be possible to readily determine at the surface which lateral wellbore or formation is producing the salt water. Additionally, there is no effective way to monitor and/or control the respective fluid flow streams to enable remedial action to be taken while maintaining the ability to reenter the multiple laterals without removal of the production hardware.
The general object of the present invention is to provide a new and improved flow segregation apparatus and method of the type described that provides separate flow channels for production fluids from respective lateral wellbores to enable monitoring and/or controlling of the fluids flowing therefrom, so as to obviate the foregoing problems with known systems.